JPH09327655A - Vibrator - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a vibrator which is excellent in resistance to an impact such as a drop and can obtain a sufficient generated force. SOLUTION: Two rectangular displacement elements 1 and 1 are bonded together, and one end side in the length direction is held by a holding member 4. Approximately parallelepiped-shaped weights 2 and 2 are adhered to both surfaces of the other end of the displacement elements 1 and 1, respectively. The weight 2 has a step at the center in the length direction on the surface facing the displacement element 1 and has a thickness of two steps. Thereby, the holding member 4 for the weight 2
A gap 3 is provided between the side half and the displacement element 1. Further, the displacement element 1, the weight 2 and the holding member 4 are covered and protected by a rectangular tubular covering body 6. Further, the displacement elements 1 and 1 are connected to the AC power source 5 at the ends on the holding member 4 side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibrator using a piezoelectric element.

[0002]

2. Description of the Related Art For example, as a built-in vibrator for calling a mobile phone or a pager, a structure in which an eccentric load is provided on a rotating shaft of a small motor has been conventionally used. Is getting However, when an electromagnetic motor is used, it is difficult to reduce the size because the structure is complicated, and there is a limit to the reduction of power consumption.

Therefore, a device using a piezoelectric material has been devised for the purpose of miniaturization and low power consumption, but it is still under development. The following actuators have been proposed as actuators using a piezoelectric material.

Japanese Unexamined Patent Publication No. 62-204885 discloses a vibration type actuator in which a piezoelectric bimorph is applied to a polishing mechanism (FIG. 8). In the piezoelectric vibrator 81, two piezoelectric films 82, 82 having different displacement directions when a voltage is applied are bonded, and electrode films 83,
It is a laminated type formed by forming 84, 84. One end side of the piezoelectric vibrator 81 is supported by a supporting portion 85, and the other end side is an actuator.
An actuator attachment portion 87 for detachably attaching the 86 is provided. A lead wire 88 is connected to the electrode film 83, and a lead wire 89 is connected to the electrode films 84 and 84.

Then, both electrode films 8 are connected through the lead wires 88 and 89.
When an AC voltage is applied between 3 and 84, the piezoelectric vibrator 81 vibrates due to the bending displacement of the piezoelectric films 82 and 82, which causes the actuator
86 swings.

Further, Japanese Patent Laid-Open No. 3-9581 discloses an actuator having a function of making the initial position of a displacement element a constant level. The displacement element of this actuator
As shown in FIG. 9, 21 is two piezoelectric ceramics 22, 22.
A metal elastic plate (23) is sandwiched between the two, and the metal elastic plates (24, 24) are provided on both outer side surfaces of the piezoelectric ceramics (22, 22). One end of the displacement element 21 has a fixed member.
It is fixed at 25, the other end is a free end, and a weight 26 that is a static load is attached. Further, the metal elastic plates 23, 24, 24 are connected to the power source at their fixed side end portions.

When a predetermined voltage is applied to the displacement element 21, the free end is displaced in the direction indicated by the hollow arrow. Thereafter, when the applied voltage is set to 0 V, the free end of the displacement element 21 returns to the initial position by its own displacement return force and the load of the weight 26. Therefore, this actuator can obtain a highly accurate displacement amount. Here, the weight, size and shape of the weight 26 are set in consideration of the displacement force of the displacement element 21, the bending strength, or the positional relationship between the displacement element 21 and the base material.

In this way, the bimorph actuator is
It is known that the generated force is weak, but a large amount of displacement can be obtained with a simple structure.When a DC electric field is applied, displacement in one direction is obtained, and when an AC electric field is applied, the force generated by displacement in both directions is Vibration can be obtained by being transmitted as a reaction force to the fixed end. The bimorph actuator uses two piezoelectric plates, but even a unimorph actuator using one piezoelectric plate can obtain the vibration effect.

[0009]

When a bimorph actuator is applied to a vibrator, a force generated by vibration is used. This force is represented by the product of the mass of the bimorph and the acceleration of vibration, and the tip of the free end is used. Is the maximum.
However, the force that can be generated by the conventional bimorph actuator is insufficient as a vibrator. In addition, when the vibrator is used in a mobile device, it is required to have sufficient resistance to impact such as dropping.

The present invention has been made in view of the above circumstances, and is provided with a covering body that covers a moving region of the weight attached to the free end of the piezoelectric element during driving.
An object of the present invention is to provide a vibrator which has excellent resistance to impact such as dropping and which can obtain a sufficient generating force.

[0011]

[Means for Solving the Problems] In general, in order to exert the function as a practical vibrator, a configuration in which a load is applied to the tip is considered, and a load of up to several tens of times the mass of the bimorph itself is applied. There is a need. However, when a load is applied to the tip, if a shock such as a drop is applied, the weight attached to the free end of the piezoelectric element largely swings, and the piezoelectric element may be largely displaced and destroyed.

Therefore, according to the first aspect of the invention, in a vibrator for vibrating by applying an AC electric field to a piezoelectric element whose one end is held by a holding member, a weight added to the free end of the piezoelectric element, and a weight when driven. And a covering member fixed to the holding member for covering an area where the weight exists.

For example, when a large impact such as a drop is applied, the piezoelectric element is displaced more than at the time of normal vibration, and this displacement amount is larger by applying a load to the tip, but the covering body is With the provision, the displacement amount at this time can be limited. This makes it possible to avoid damage to the piezoelectric element or a decrease in durability.

According to a second aspect of the present invention, in the first aspect, a buffer layer is formed on the inner surface of the cover.

When a large shock is applied and the piezoelectric element is displaced more than during normal vibration, the weight may collide with the covering body and the shock may be applied to the piezoelectric element depending on the size of the covering body. However, since the buffer layer absorbs the shock at this time, the shock received by the piezoelectric element can be alleviated and the shock resistance is improved.

According to a third aspect of the present invention, in the first or second aspect, the covering is large enough to cover a region larger than a moving region of the weight during driving. .

It is possible to prevent the piezoelectric element from being broken or the weight from falling off due to an impact caused by the weight coming into contact with the covering during normal vibration.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a vertical cross-sectional view showing a vibrator according to the present invention. Two rectangular displacement elements 1 and 1 are bonded together, and one end side in the length direction is held by a holding member 4. Approximately parallelepiped-shaped weights 2 and 2 are adhered to both surfaces of the other end of the displacement elements 1 and 1, respectively. The weight 2 has a step at the center in the length direction on the surface facing the displacement element 1 and has a thickness of two steps. As a result, a gap 3 is provided between the half of the weight 2 on the holding member 4 side and the displacement element 1. Further, the displacement element 1, the weight 2 and the holding member 4 are covered and protected by a rectangular tubular covering body 6. Further, the displacement elements 1 and 1 are connected to the AC power source 5 at the ends on the holding member 4 side. FIG. 2 is a perspective view showing a state in which the cover 6 is removed.

FIG. 3 is an enlarged sectional view showing a bonded portion A of the displacement elements 1, 1. The displacement element 1 is a piezoelectric ceramic
Electrodes 12 and 12 are formed on both surfaces of 11, and the two displacement elements 1 and 1 are bonded together with a metal plate 13 interposed therebetween.

[0020]

EXAMPLE A vibrator according to the present invention can be manufactured as follows. [Example 1] A piezoelectric material containing lead zirconate titanate as a main component was fired, processed into a thin plate (piezoelectric ceramic 11) with a width of 10 mm, a length of 20 mm and a thickness of 200 µm, and gold-plated on both sides to form an electrode with a thickness of 10 µm. Two displacement elements 1 in which 12 and 12 are formed and polarized are manufactured. These two displacement elements 1 have a width of 10 mm and a length of 25
5 mm long on both sides of a brass metal plate 13 mm, 50 μm thick
Leaving the above, and bonding with an adhesive so that the polarization directions are the same. Then, the exposed electrodes 12 of the piezoelectric ceramics 11 are electrically connected to the AC power source 5, respectively, and a driving power can be supplied between the exposed electrodes 12 and the metal plate 13 made of brass to prepare a bimorph. The exposed end of the metal plate 13 is clamped by the holding member 4 from both sides.

On the other hand, in order to prepare the weight 2, two lead rectangular parallelepipeds each having a width of 10 mm, a length of 10 mm and a thickness of 1.5 mm are prepared, and each of the half portions in the length direction on one side has a thickness of 1.0 mm. Cut so that Then, an adhesive is applied to the one surface side of the half portion having a thickness of 1.5 mm, and is adhered and fixed to the free end side of the bimorph which is not held by the holding member 4 so that the thin portion becomes the holding member 4 side. To do.

Next, a rectangular tubular stainless steel covering 6 having a width of 12 mm, a length of 30 mm and a height of 6 mm is prepared, and an adhesive is used inside one of the openings to hold the bimorph holding member. Four
Adhesively fixed. Although a piezoelectric material such as lead zirconate titanate is generally used for the bimorph, it is not limited to this. For the weight 2, a material having a large specific gravity is suitable for reducing the volume. Further, the bimorph and the weight 2 may be fixed with screws,
Adhesion is preferred, which requires no machining.

[Second Embodiment] FIG. 4 is a vertical sectional view showing a vibrator according to a second embodiment. The vibrator of Example 2 is manufactured as follows. That is, the weight 2 is attached to the same bimorph as in the first embodiment, and is held by the holding member 4. On the other hand, on the inner surface of the cover 6, a polyurethane resin having a thickness of 0.5 mm is coated at a position corresponding to the periphery of the weight 2 to form a buffer layer 7, and the inner surface of the opening of the cover 6 holds the bimorph. The member 4 is adhesively fixed. The material of the buffer layer 6 is not limited to polyurethane resin.

Drop tests and continuous drive tests were carried out to evaluate the impact resistance and endurance of the vibrators of Examples 1 and 2, and the results were compared with those of Comparative Examples 1 and 2. For two types of drop test and continuous drive test,
Three vibrators of each of Examples 1 and 2 and Comparative Examples 1 and 2 were prepared.

In the drop test, the vibrator, whose generated force has been measured in advance, is placed in the longitudinal direction, the width direction and the thickness direction of the vibrator.
After dropping each time from a height of 2M or 4M onto the concrete floor surface, the generated force was measured again. Then, it was disassembled and the presence or absence of cracks in the displacement element 1 (piezoelectric ceramic 11) made of ceramics was investigated. The continuous drive test was performed by measuring the generated force in advance in a vibrator at 100 ° C in an atmosphere of 20 ° C.
Applying an AC electric field of V and continuously driving for 10 hours, then
The generated force was measured again to investigate the output change. Displacement element 1 (piezoelectric ceramic 1
The presence of cracks in 1) was investigated. The generative force was determined as follows. That is, 100 g of a measuring weight and a bimorph are installed on a spring scale to form a resonance system, an AC electric field of maximum 100 V is applied to the bimorph to cause resonance, and the maximum acceleration is measured by an accelerometer installed on the scale. Then, it was determined from the product of this measurement result and the measurement load.

As shown in FIG. 5, the vibrator of Comparative Example 1 uses the same bimorph as that of Examples 1 and 2, and the covering 6 is not attached. Then, at the time of measurement, it was placed on the balance only on the fixed end portion with a metal holding member interposed therebetween so as to float 3 mm. As shown in FIG. 6, the vibrator of Comparative Example 2 was obtained by adhering and fixing the same bimorph as in Examples 1 and 2 to the inside of a stainless steel covering 8 having a width of 12 mm, a length of 30 mm and a height of 4 mm. is there. The buffer layer 7 is formed on the inner surface of the cover 8 as in the second embodiment.

In Examples 1 and 2, the tip of the weight 2 did not come into contact with the coating 6 and the buffer layer 7 during driving, but in Comparative Example 2, the tip of the weight 2 was formed on the inner surface of the coating 8. It was in contact with the buffer layer 7. FIG. 7 is a vertical cross-sectional view showing a state where the weight 2 is in contact with the covering body.

[0028]

[Table 1]

Table 1 shows the above Examples 1 and 2, Comparative Examples 1 and 2.
The result of the 2M drop test in is shown. As is clear from Table 1, the breakage due to the 2M drop test was not confirmed in Examples 1 and 2, and Comparative Example 2, but in Comparative Example 1, transverse cracking was confirmed at the fixed end because it was not protected by the covering. It was
It is considered that this is because the load was concentrated near the fixed end when dropped. The generated force after the test was almost the same as that before the test in Examples 1 and 2 and Comparative Example 2, but was significantly decreased in Comparative Example 1 due to breakage. Further, in Comparative Example 2, the output was large before and after the test, which is considered to be because the weight 2 collided with the covering 8 during driving.

[0030]

[Table 2]

Table 2 shows the results of the 4M drop test. As is clear from Table 2, as a result of the 4M drop test, in Example 1 and Comparative Example 1, a transverse crack was confirmed at the fixed end and in Comparative Example 2, a transverse crack was confirmed at the central portion, but in Example 2, it was damaged. Was not confirmed. It is considered that this is because the shock at the time of dropping was alleviated by the buffer layer 7. The generated force after the test was significantly reduced in Examples 1 and Comparative Examples 1 and 2 in which breakage was observed, but there was almost no change in Example 2 in which breakage was not observed.

[0032]

[Table 3]

Table 3 shows the results of the continuous drive test. As a result of the continuous drive test, breakage was not confirmed in Examples 1 and 2 and Comparative Example 1, but in Comparative Example 2, a transverse crack was generated at the fixed end. It is considered that this is because the shock when the weight 2 comes into contact with the cover 8 propagates to the displacement element 1 (piezoelectric ceramic 11) made of ceramics, and the repetition causes destruction. Therefore, in Comparative Example 2, the output after continuous driving was significantly reduced.

The vibrator according to the present invention may be a pager or the like.
When applied to a mobile device, a structure that can withstand a 2M drop test is sufficiently practical in consideration of human extension.

The present invention is not limited to a bimorph using two piezoelectric ceramics, but a unimorph may be used, for example. However, it goes without saying that a larger generative force can be obtained when a bimorph is used.

[0036]

As described above, since the vibrator according to the present invention is provided with the covering body around the weight added to the free end of the piezoelectric element, the vibrator has good resistance to impact such as dropping.
When the buffer layer is formed on the inner surface of the covering body, for example, a shock applied to the piezoelectric element when it is dropped is mitigated, so that the shock resistance is further improved. In the case where the cover has a size capable of covering a region larger than the moving region of the weight during driving, the present invention has excellent effects such as a decrease in endurance can be avoided.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a vibrator according to the present invention.

FIG. 2 is a perspective view showing a vibrator with a cover removed.

FIG. 3 is an enlarged cross-sectional view showing a bonded portion of the two displacement elements of FIG.

FIG. 4 is a vertical cross-sectional view showing another vibrator according to the present invention.

5 is a vertical cross-sectional view showing a vibrator of Comparative Example 1. FIG.

FIG. 6 is a vertical cross-sectional view showing a vibrator of Comparative Example 2.

FIG. 7 is a vertical cross-sectional view showing a state in which the weight contacts the covering body.

FIG. 8 is a cross-sectional view showing a conventional example (actuator for a polishing machine) using a bimorph.

FIG. 9 is a side view showing another conventional example (actuator) using a bimorph.

[Explanation of symbols]

 1 Displacement Element 2 Weight 4 Holding Member 5 AC Power Supply 6 Cover 7 Buffer Layer 11 Piezoelectric Ceramic

Claims (3)

[Claims] 1. A vibrator for obtaining an oscillation by applying an AC electric field to a piezoelectric element, one end of which is held by a holding member,
A vibrator comprising: a weight added to a free end of the piezoelectric element; and a cover body that covers a region where the weight exists during driving and is fixed to the holding member. 2. The vibrator according to claim 1, wherein a buffer layer is formed on the inner surface of the cover. 3. The vibrator according to claim 1, wherein the covering body has a size capable of covering a region larger than a moving region of the weight during driving.